COMBUSTION AND EMISSIONS OF LOW HEAT REJECTION CERAMIC METHANOL ATAC ENGINES

When methanol is used as fuel for internal combustion engines, formald ehyde and unburned methanol emissions can be a problem. To overcome th is shortcoming, an engine with the active thermo-atmosphere combustion (ATAC) system was proposed, along with improvements in heat-insulatin g performance and the realization of high-temperature combustion by us ing ceramics for the combustion chamber walls. The combustion and emis sions characteristics of this ceramic low heat rejection (LHR) methano l ATAC engine were investigated. Combustion performance was compared b etween operation with methanol and gasoline. When methanol was used, i t was seen that the ATAC operation region was widened considerably. Al so, a reduction in aldehyde emissions was achieved, due to the high-te mperature operation of the combustion chamber. However, efficiency det eriorated at times due to early self-ignition timing. This was overcom e by the use of lean fuel-air ratios, which resulted in both a reducti on of NOx and an improvement in fuel consumption. With a premixed fuel supply system, wall surface ignition was unavoidable for combustion c hamber surface temperatures greater than 800 K (527 degrees C). Wall s urface temperature swing and instantaneous heat flux increased substan tially with ATAC operation under these conditions.